Medical ventilation devices (also referred to as ventilators, respiration devices and respirators) are well known. The operation of a medical ventilation device for breathing assistance to a patient is controlled via the pressure or the volume of the respiratory gas. The medical ventilation device has a pressure sensor and a flow sensor in order to make this control effective. With a properly placed flow sensor (usually close to the mouth of the patient), it is possible to measure the inspiratory flow and/or the expiratory flow.
An example of such a portable medical ventilation device is the Oxylog® 3000 manufactured by Dräger Medical A.G. The Oxylog® 3000 offers sophisticated ventilation for patients in emergency situations and during transport in and between hospitals. Designed to support a wide range of patients with various medical conditions, the Oxylog® 3000 offers volume-based and pressure-based operational modes for controlled, synchronized or assisted ventilation. When transporting, e.g., critical-care patients, from the ambulance to the Intensive Care Unit at the hospital, the need of interrupting ventilation therapy is therefore eliminated. Clear flow curves and pressure curves are shown on a high-contrast display, offering reliable patient monitoring.
In operational use, a medical ventilation device is coupled to a patient via a hose system. A medical ventilation device can be configured for operating with different hose systems. Different categories of patients require that different types of hose systems be used. Patients can be categorized on the basis of, e.g., the age of the patient (e.g., young versus adult), and/or the type of medical condition of the patient. An optimum performance of the medical ventilation device requires that the hose system being used match the selected operating mode of the medical ventilation device.
What type of hose system is selected in operational use depends on the type of patient and on the ventilation mode. Also, the type of flow sensor that forms part of the hose system can depend on the type of patient. For these reasons, different types of hose systems are characterized by different combinations of flow sensors and hoses, depending on, e.g., the required accuracy of the measurements of the flow, the hose's resistance to the flow; the hose's compliance; the amount of dead space of the hose; whether the hose is a re-usable hose or a disposable hose, etc. In the case of small children, the tidal volume of the respiratory gas is small and, therefore, the dead space of the hose is very critical.
Therefore, a medical ventilation device is usually optimized and calibrated for use with one or more specific hose systems, and the performance of the medical ventilation device can only comply with the device's specification if these specific hose systems are being used. The use of hose systems, other than the selected hose systems for which the medical ventilation device has been optimized and calibrated, can affect the performance of the medical ventilation device and may even lead to dangerous situations. For example, the pressure of the respiratory gas in the hose system or the volume of the respiratory gas delivered to the patient per unit of time, could become higher than the value set by the operator in the user interface of the medical ventilation device. This is especially a point of attention if the patient is a small child.
There can be various reasons why the hose system being used does not match with the ventilation therapy of the patient in a specific case. One of the reasons may be the following. For example, the medical ventilation device and the hose system have been prepared for a standard-type patient, which is typically an adult patient. If it turns out that the actual patient is a small child instead, this hose system must be replaced by another one prior to use, and the other hose system must be reselected at the medical ventilation device so that the medical ventilation device is properly set. However, in a stressful situation it is easily forgotten to replace and/or reselect the hose system. Another reason may stem from the fact that an operator is less familiar with the ventilation device or is only familiar with a certain type of hose system. If this familiar type of hose system is not the proper one for the set ventilation therapy, a hazardous situation may arise.
Typically, a hose system comprises a hose as a conduit for the respiratory gas, and a flow sensor. The flow sensor of the hose system measures the inspiratory flow and/or the expiratory flow through the hose, and is usually located close to the patient. This flow sensor forms an integral part of the hose system.
For completeness, the expression “dead space” is used, within the context of ventilation therapy, to refer to the volume of gas that is not refreshed for oxygen and for carbon dioxide after exhalation and that is again inhaled by the human body while breathing.